Ring
The heart of the CRYRING facility is an ion synchrotron and storage ring
with 51.6 m circumference. It has twelve straight sections and six
superperiods. Six of the straight sections have focusing magnets
(quadrupoles and sextupoles) and correction dipoles in them, the other
six are used for injection, acceleration, diagnostics, electron cooling,
a gas-jet target, and the last one for other experimental equipment. The
lattice functions are shown in the figure.
The injection is made electrostatically, using four pairs of deflection
plates creating a local closed-orbit bump on the injection straight
section only. The injection takes place over 10 turns, filling up the
horizontal acceptance of 200 pi mm mrad. The vertical acceptance is
100 pi mm mrad.
The ions are accelerated by a driven drift tube - a 2.7 m long drift
tube which is connected to a broad-band amplifier. The maximum voltage
on the drift tube is 7 kV at frequencies between 40 kHz and 1.5 MHz.
The magnet power supplies can be run in two modes, fast or slow. In
the fast mode, the acceleration to full energy takes 150 ms, while in
the slow mode, ramping to full energy is made in 1 s or more. The
maximum energy, set by the 1.44 Tm rigidity of the ring, is
96 (q/A)2 MeV/u.
Diagnostics, scattered all over the ring, consist of Faraday cups for
finding the beam at injection; electrostatic pickups for measurements
of beam intensities, closed-orbit distortions, Q values, etc.; a
Schottky pickup; a horizontal and a vertical residual-gas beam-profile
monitor; an AC and a DC current transformer for absolute measurements
of beam currents; and particle detectors detecting charge-changed ions.
The electron
cooler cools the stored ion beam, i.e., it reduces its velocity spread
both transversally and longitudinally. It also acts as an electron
target for studies of recombination between the stored ions and
electrons.
Ultra-high vacuum is important for operation of the ring. The true
hydrogen pressure is approximately 1x10-11 torr (which
means that the nitrogen-equivalent pressure is less than
7.5x10-12 torr). Pumping is done mainly through NEG
(Non-Evapourable Getter) pumps, and also ion pumps, turbo-molecular
pumps and cryopumps.
A good vacuum is essential for long beam lifetimes. These range from
milliseconds to weeks and more, depending on the type of ion, its
energy and its charge state. The diversity of ions that have been
stored and in most cases also accelerated in the ring can be
appreciated from this
list.
The operation of the CRYRING facility for physics experiments was ended in December 2009.
It will be taken out of use in the spring of 2010, after some concluding tests related to the
planned transfer of the ring to FAIR in Darmstadt.
2010-03-18
